 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.internal.expressions;

 import org.eclipse.core.expressions.EvaluationResult;
 import org.eclipse.core.expressions.Expression;
 import org.eclipse.core.expressions.ExpressionInfo;
 import org.eclipse.core.expressions.IEvaluationContext;
 import org.eclipse.ui.ISources;
 import org.eclipse.ui.internal.services.SourcePriorityNameMapping;

 /**
  * <p>
  * An expression representing the <code>part id</code> of the legacy editor
  * action bar contribution.
  * </p>
  * <p>
  * This class is not intended for use outside of the
  * <code>org.eclipse.ui.workbench</code> plug-in.
  * </p>
  *
  * @since 3.2
  */
 public class LegacyEditorActionBarExpression extends Expression {
     /**
      * The seed for the hash code for all schemes.
      */
     private static final int HASH_INITIAL = LegacyEditorActionBarExpression.class
             .getName().hashCode();

     /**
      * The identifier for the editor that must be active for this expression to
      * evaluate to <code>true</code>. This value is never <code>null</code>.
      */
     private final String activeEditorId;

     /**
      * Constructs a new instance of <code>LegacyEditorActionBarExpression</code>
      *
      * @param editorId
      * The identifier of the editor to match with the active editor;
      * must not be <code>null</code>
      */
     public LegacyEditorActionBarExpression(final String editorId) {

         if (editorId == null) {
             throw new IllegalArgumentException (
                     "The targetId for an editor contribution must not be null"); //$NON-NLS-1$
 }
         activeEditorId = editorId;
     }

     public final void collectExpressionInfo(final ExpressionInfo info) {
         info.addVariableNameAccess(ISources.ACTIVE_PART_ID_NAME);
         info
                 .addVariableNameAccess(SourcePriorityNameMapping.LEGACY_LEGACY_NAME);
     }

     protected final int computeHashCode() {
         int hashCode = HASH_INITIAL * HASH_FACTOR + hashCode(activeEditorId);
         return hashCode;
     }

     public final boolean equals(final Object object) {
         if (object instanceof LegacyEditorActionBarExpression) {
             final LegacyEditorActionBarExpression that = (LegacyEditorActionBarExpression) object;
             return activeEditorId.equals(that.activeEditorId);
         }

         return false;
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.core.expressions.Expression#evaluate(org.eclipse.core.expressions.IEvaluationContext)
      */
     public final EvaluationResult evaluate(final IEvaluationContext context) {
         final Object variable = context
                 .getVariable(ISources.ACTIVE_PART_ID_NAME);
         if (equals(activeEditorId, variable)) {
             return EvaluationResult.TRUE;
         }
         return EvaluationResult.FALSE;
     }

     public final String toString() {
         final StringBuffer buffer = new StringBuffer ();
         buffer.append("LegacyEditorActionBarExpression("); //$NON-NLS-1$
 buffer.append(activeEditorId);
         buffer.append(')');
         return buffer.toString();
     }
 }

